优化：编辑器点击富文本框，提示语不消失

src/components/RichText.vue

@@ -553,6 +553,29 @@ export default {
           //     this.$emit('selectContentSetMemo', null, annotationId);
           //   }
           // });
+
+          editor.on('focus', () => {
+            const body = editor.getBody();
+            if (body && body.hasAttribute('data-mce-placeholder')) {
+              body.removeAttribute('data-mce-placeholder');
+            }
+          });
+          editor.on('blur', () => {
+            const body = editor.getBody();
+            const content = editor.getContent({ format: 'text' }).trim();
+            if (body && !content && this.placeholder) {
+              body.setAttribute('data-mce-placeholder', this.placeholder);
+            }
+          });
+          editor.on('input', () => {
+            const body = editor.getBody();
+            const content = editor.getContent({ format: 'text' }).trim();
+            if (body && content && body.hasAttribute('data-mce-placeholder')) {
+              body.removeAttribute('data-mce-placeholder');
+            } else if (body && !content && !body.hasAttribute('data-mce-placeholder') && this.placeholder) {
+              body.setAttribute('data-mce-placeholder', this.placeholder);
+            }
+          });
         },
         font_formats:
           '楷体=楷体,微软雅黑;' +